Spontaneous Rupture of Arachnoid Cyst in a Child: A Rare Case Report

An arachnoid cyst is a benign lesion filled with cerebrospinal fluid that usually develops in the middle cranial fossa. The arachnoid cyst may become symptomatic if it has a large size or when it gets ruptured. Spontaneous rupture of an arachnoid cyst is a very rare complication. We report the case of an 11-year-old girl who was brought to the emergency department with a complaint of a progressive headache that was associated with vomiting. On examination, she was found to have papilledema. Subsequently, magnetic resonance imaging of the brain was performed to exclude any space-occupying lesion. The scan demonstrated a right extra-axial temporal lesion, measuring 7.8 x 5.4 x 4.9 cm on maximum dimensions, along with an extension to the right cerebral convexity in a crescentic shape. The lesion follows the signal intensity of cerebrospinal fluid on all sequences and exhibited no post-contrast enhancement or restricted diffusion. The lesion exerted a mass effect in the form of compression of the right temporal lobe. These findings were consistent with an arachnoid cyst with subdural hygroma. The patient was referred to the neurosurgery team. Then, the right temporal arachnoid cyst was drained through the right temporal craniotomy and the subdural hygroma was drained through a frontal Burr hole. The patient was seen after one month in the pediatrics clinic and was completely asymptomatic.


Introduction
An arachnoid cyst is a congenital extra-axial cystic lesion containing cerebrospinal fluid between arachnoid sheets with no communication with the ventricular system. It represents around 1% of all intracranial masses [1]. It can be seen in different locations such as the quadrigeminal and suprasellar cisterns, posterior cranial fossa, and along the cerebral convexity. However, the most common location of an arachnoid cyst is the middle cranial fossa, occurring in over 50% of cases. While the majority of patients with arachnoid cysts are asymptomatic, arachnoid cysts may present with headaches, seizures, and neurological deficits [2]. Arachnoid cysts may get ruptured in the setting of head trauma. Spontaneous rupture of arachnoid cysts is very unusual [3]. Here, we report the case of a young girl with spontaneous rupture of an undiagnosed arachnoid cyst.

Case Presentation
We present a case of an 11-year-old girl who was brought to the emergency department by her parents with a complaint of progressive headache. The headache was in the occipital region bilaterally. It started one month before the presentation and gradually increased in severity. She described the headache as sharp in nature. The headache was non-radiating, and it was worse in the morning. The parents reported that the headache became associated with multiple episodes of vomiting over the past few days. They visited a number of pediatric clinics, and the child was offered simple analgesics with non-steroidal antiinflammatory drugs. The patient was not known to have any medical conditions. She had no previous surgeries. She was up-to-date on the national vaccination schedule. There was no family history of migraine.
On physical examination, the child appeared to be in pain. There were no signs of respiratory distress. Her vital signs were within the normal range, including a pulse rate of 80 beats/min, a respiratory rate of 18 breaths/min, a blood pressure of 98/54 mmHg, and a normal temperature of 37.0 °C. Neurological evaluation revealed normal findings of the cranial nerves, apart from bilateral papilledema. Examination of the upper and lower extremities showed normal tone, power, reflexes, and coordination. There was no weakness or sensory loss noted on examination.
Considering the concerning features of headache, a head computed tomography scan was planned to exclude any space-occupying lesion. Despite discussing the importance of this investigation, the parents strongly refused due to the fear of radiation exposure. Then, the patient underwent brain magnetic resonance imaging. The scan demonstrated a right extra-axial temporal lesion, measuring 7.8 x 5.4 x 4.9 cm on maximum dimensions, along with an extension to the right cerebral convexity in a crescentic shape. The lesion follows the signal intensity of cerebrospinal fluid on all sequences and exhibited no post-contrast enhancement or restricted diffusion. The lesion exerted a mass effect in the form of compression of the right temporal lobe. There was no midline shift or evidence of herniation. No evidence of acute infarction or hemorrhage was noted. The findings were suggestive of an arachnoid cyst in the right middle cranial fossa with a rupture into the subdural space (Figures 1-2).

FIGURE 1: Sagittal brain MRI images show a cystic lesion in the temporal region (thick arrow) with extension along the cerebral convexity (thin arrow), which demonstrates a high signal on the T2weighted image (A) and a low signal on the T1-weighted image (B)
MRI: magnetic resonance imaging The diagnosis was discussed with the parents, and the patient was referred to the neurosurgery team for further management. The right temporal arachnoid cyst was drained through the right temporal craniotomy. The subdural hygroma was drained through a frontal Burr hole. The drained cerebrospinal fluid was sent for